Leaky tin roof coating?

Got an addon to the barn that leaked like a sieve this week with the rain we got. It has always had a few drips but this time I had 10 buckets around my work bench area and another 6 spread around. It is running down mainly 2 seams of corrugated tin and then dripping in at each 2x4 runner across the roof. Last year I went up with some clear silicone roofing caulk and caulked the seams and some of the screws.

The part that is added on is 32' wide with a 24' long roofing run. There is a 6' rise over the the 24' so is a 4:1 slope. Has two skylight panels in it. The screws are screwed into the high portions of the corrugations. Mostly no rust except a little below the 2 skylight panels.

Wondering what is the best coating to put on it but don't want to coat the whole barn or put any black stuff on it. The barn roof is fairly steep and in good condition so don't want to get into too much of a color mismatch. I've used the mobile home stuff before on flat roofs. I don't have anything that will spray thick stuff and if I brush the stuff on then I wonder if it will tend to fill in the corrugations. I'd like to buy an airless sprayer some day, just need a good reason to get one.

What do you guys recommend? None of that stuff is very cheap. Got more rain on the way and will probably hang a tarp underneath and direct the drips away from the bench.

24 feet of metal will expand and contract a lot with different temps. I'm
guessing the screws have made bigger holes in your metal.
BIL paid a guy to replace all his screws.
Then he ran 2x4 over old roof and put a new roof on.

good luck.
Report back what you find is your problem.
geo.

Not sure I follow, but if there arent holes in the roofing the coating wont fix the issue. It sounds like there is a specific spot or two that needs attention and not the entire roof. If it were the screw heads I would just replace them, but it doesnt sound like thats the case. Again, I may not completely understand.

First you have to figure out the problem. Is it at the seams and are they properly lapped? Is it the seals on the screws? Has there been some damage that needs fixing? Is it a flashing issue maybe? Is it as simple as loose screws? A good steel roof with the pitch you outline shouldn't leak at all until something either backs up (ice, gutters) or something loosens up badly. Start at square one. Putting roof coat on isn't likely to fix the actual problem.

Fibered aluminum roof coating is what I have used on old rusty metal for years.
It ain't cheap and has to be stirred a lot as you put it on.
It is thick enough to fill small holes and seams that leak.
Also seals well around screws or nails.
I have used a lot of used metal over the years and it works well for me.
I had a place above the chimney on my shop that leaked.
I sprayed that stupid new stuff and used tar and until I put on the fibered aluminum, I was wasting my time.
Richard in NW SC

It's not the screws or the screw holes from what I see. The seams are properly lapped over two seams which is how it is designed. This is the narrow grooved tin and the big box stores now sell the wider stuff. The water is running down the seams and still managing to cross over. You guys got me thinking it could be a little loose at the seams so I might try adding an extra set of screws along the seams with the impact wrench. I can post a pic later.

I had a leak on the house roof that I have struggled with for years.Tried some of those Flex(liquid;paste;tape) products. It worked!No more leacks. Now I can properly fix the ceiling.You can get
it in white and (I think) silver.

(quoted from post at 15:10:30 03/20/21)
I might try adding an extra set of screws along the seams with the impact wrench. I can post a pic later.

Click to expand...

Go easy on the tightening, you want the washers to slightly compress but not be "mashed". Otherwise you may have more leaks. Modern method is to screw into the flat rather than the rib.

Good info here: https://www.metalroofingsource.com/install-metal-roofing-fasteners/

Most of the time when a metal roof leaks it's because there isn't enough slope on the roof to carry the water off. The water then runs under where the tin overlaps and leaks. It doesn't matter what kind of sealant you put on the seams the metal expands and contracts
so much it breaks the sealant and lets water through. Then the nails or screws start coming out which allows more water through.

You might want to add butyl rubber sealant tape under the overlap and then install new screws.

You should also use new screws that have bigger diameter thread and longer than old screws to grip old hole in wood.
And get them with oversized washers as well if needed.

Like others have said try to fix the cause, then coat with a
product like nnalert silver seal 300. Its a fibered aluminum
roof coating that stays somewhat flexible and can handle
some expansion and contraction. Ive had good luck with it.

I will add that silicon caulk is usually not compatible with rubber/tar based sealants, and curls/delaminates. So putting those two together
might also be an early failure point. Jim

OK. You guys are getting this figured out. I can pull the side screws, loosen some others and run some butyl tape. That should get a waterproof seal. This corrugated tin doesn't really have a flat on it as it is a constant wave. Coating will be a last resort.

Not sure I quite agree with the screws in the flat modern thinking but it may have to do with the lack of hold down force in the high ridges of this new style roofing and then it is hard to get it just right without denting the ridge or leaving it loose. I'd consider the hidden screws though. Used to do some contract steel work and cousin did it for years. It's all about how fast you can get the job done as they pay contractors by the square and not the hour. We used electric impact wrenches and it didn't take long after all the sheets are predrilled on the ground. Now they have battery impacts and screws that drill.

Depending on how "pointy" the ridge is, the rubber washer might only be pushing on the pointy party and not at all on the slopes.

Old fashioned big wave corrugated might not have enough curve in the wave to be detrimental to the washer getting it to seal.

Use Water Cut-off mastic to caulk the seam.

https://www.mulehide.com/Roofing-Products/p/WaterCutOffMastic

I use Permatex ultra grey RTV are ultra with copper with good luck around the screws. I have one roof it has stayed on well for over 10 years.

You will have to stay at it to get the leak stopped... BTW I am having the skylights took out of a few buildings this year...

There is a product called through the roof that comes in bulk or caulking tube. It can be painted on with a brush, or applied with a putty knife. It is clear, sticky as heck and best of all it stays
CLEAR. They claim it can be applied to a wet surface, I haven't tried that. I have used it on several roofing applications though and it is all I hoped it would be. Pricey, but can be found at Lowe's or
most hardware stores.

Went to Lowest yesterday. The butyl rubber mastic stuff I was looking for was special order. Me and the lowes guy walked all over to the various sections and they didn't have any tubes that said butyl rubber and we both remembered seeing it before. I ended up getting 4 tubes of this one brand of flexible rubber sealer at 10 bux each. Since I'm going to unscrew the seams anyway, I can slide a couple chisels under and this time get a good bead of that roofing sealer up under that first overlap. Will see how it goes. Had to make a road trip yesterday anyway to get a half barrel of blacksmithing coal.

That mastic tape will go in under the lap seams and seal them. I have used the silicone sealant not the caulk stuff when we put dads garage roofing on . WE run a bead right down the laps then put the next sheet on and repeated on the next seam. Has not leaked yet been 10 years now probably. My brother reroofed a shed with 40 foot long sheets they used the mastic tape on them with no leaks. they used it on all the lap seams. No all our roofs have 24 ga steel that helps a lot for stiffness to start screws and all screws are on the top of the rib/bump no matter what pattern is used.